This invention relates to a drive and control system employing dual cams to produce high speed intermittent motion. More particularly, this invention relates to a drive system generator consisting of one or more intermittent motion generators, controlled by a programmable logic controller.
Intermittent motion generation is useful in cutting, shearing, or pressing machines. Intermittent motion is also useful where intermittent strokes are required. Processes such as cutting to length sheet metal use this type of stroke. The cutting strokes are generated by a combination of driving means coupled to a rotating camshaft, which is in turn coupled to a Pitman arm, or a ram attached either to shears or to a press. Most current drive systems employed for sheet metal processing equipment operate on the principle of stopping the assembly of the camshaft, Pitman arm and ram after each operating cycle. This means that the camshaft will rotate precisely 360xc2x0 after each stroke. There can be various reasons for requiring the stopping and starting of these angular cycles. One of these is to ensure not only accurate indexing requirements but also the repeatability of the motion after each stroke. Although some of the current equipment does perform well, the number of strokes are still subject to the start-stop cycle. The stop and start cycle hinders the intermittent motion rotary system that carries all the associated high cyclic inertia loads. In addition, the stroke displacement of the machine is restricted to a single cam motion. In order to generate intermittent motion at higher speeds, the drive system must run at a higher rate of revolutions per minute (RPM).
The present invention seeks to overcome the above shortcomings by providing a system for intermittent motion generation using a dual cam arrangement to increase the speed of motion generated.
The present invention seeks to provide a system for high speed intermittent motion. The system consists of one or more intermittent motion generators. Each motion generator may function independently of the others and may be controlled by a programmable logic controller (PLC). Each motion generator consists of a first and a second drive system with each drive system having its own control software and control input information received from the PLC. Each motion generator employs dual cams with fixed angular rotation. The dual cam combination consists of a first cam nested within a second cam. The dual cams permit independent and individual motion generation for each motion generator. The use of dual cams enables the system to generate different linear strokes for each generator. The angular rotation of the second cam relative to the angular rotation of the first cam causes a linear displacement which generates intermittent linear motion for each individual motion generator. The second drive system is considerably smaller than the first drive system, since the second drive train and second motor are used only for adjustments. The overall smaller system allows for an advantageously faster response time and better motion control.
The applications of the present invention are diverse. The drive system may be applied to many high-speed mechanical functions, including high-speed shearing, and pressing, packaging lines, and textile manufacturing.
In a first aspect, the present invention provides a system for intermittent motion generation for a cam follower, the system including:
(a) a first cam coupled to a first driving means, the first cam rotating about a first fixed axis;
(b) a second cam coupled to a second driving means, the second cam rotating about a second axis, the second cam having a cam-shaped cavity with the first cam being nested within the cavity;
(c) a cam follower having one end in contact with the second cam, the cam follower being linearly displaced due to an intermittent linear motion generated by a rotation of the second cam relative to a rotation of the first cam.
In a second aspect, the present invention provides a drive system for generating intermittent motion, the drive system including:
(a) first driving means;
(b) first output shaft rotatably driven by the first driving means;
(c) second driving means coupled to the first driving means;
(d) at least two cams, the at least two cams including:
(d1) a first cam rigidly mounted onto the first output shaft and having a cam-shaped outer surface;
(d2) a second cam having a cam-shaped inner surface, the second cam being mounted onto the first cam by radial bearing means, the radial bearing means being seated between the cam-shaped outer surface of the first cam and the cam-shaped inner surface of the second cam, the second cam being rotated by the second driving means;
(e) a cam follower in contact with the outer surface of the second cam, the cam follower being displaced linearly by the intermittent linear motion generated from a relative rotation of the at least two cams.